High CoR golf ball using zinc dimethacrylate

ABSTRACT

The present invention is directed to resilient golf balls and portions thereof including compositions containing zinc dimethacrylate and zinc pentachlorothiophenol, and methods for making same. In particular, the present invention is directed to a golf ball having at least one of a center, cover, or intermediate layer that includes a reaction product that includes a resilient polymer component, a free radical source, zinc dimethacrylate and at least one halogenated organosulfur compound having the following general formula I: 
     
       
         
         
             
             
         
       
         
         
           
             where R 1 -R 5  can be substituted or unsubstituted C 1 -C 8  alkyl groups; halogen groups; thiol groups (—SH), carboxylated groups; sulfonated groups; and hydrogen; in any order.

FIELD OF THE INVENTION

The present invention relates to the use of zinc dimethacrylate in golfball compositions. In particular, the invention relates to resilientgolf balls and portions thereof including compositions containing zincdimethacrylate and zinc pentachlorothiophenol, and methods for makingsame.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into several general classes: (a)solid golf balls having one or more layers, and (b) wound golf balls.Solid golf balls include one-piece balls, which are easy to constructand relatively inexpensive, but have poor playing characteristics andare thus generally limited for use as range balls. Two-piece balls areconstructed with a generally solid core and a cover and are generallypopular with recreational golfers because they are very durable andprovide maximum distance. Balls having a two-piece construction arecommonly formed of a polymeric core encased by a cover. Solid golf ballsalso include multi-layer golf balls that are comprised of a solid coreof one or more layers and/or a cover of one or more layers. These ballsare regarded as having an extended range of playing characteristics.These balls are generally easy to manufacture, but are regarded ashaving limited playing characteristics.

A variety of golf balls designed to provide a wide range of playingcharacteristics, i.e., the compression, velocity, “feel,” and spin, thatcan be optimized for various playing ability, are known in the priorart. Typical golf ball construction includes a core formed frompolybutadiene that is chemically crosslinked with zinc diacrylate and/orother similar crosslinking agents.

However, it is desirable to have golf ball compositions that includealternative crosslinkers, such as zinc dimethacrylate, withoutcompromising golf ball payability. The compositions of the presentinvention provided golf balls with improved coefficient of restitution(“CoR”) and increased compression using zinc dimethacrylate.

SUMMARY OF THE INVENTION

The present invention is directed to a golf ball comprising at least onestructural layer formed from a composition that comprises a resilientpolymer component, a free radical source, zinc dimethacrylate and atleast one halogenated organosulfur compound having the following generalformula I:

where R₁-R₅ can be substituted or unsubstituted C₁-C₈ alkyl groups;halogen groups; thiol groups (—SH), carboxylated groups; sulfonatedgroups; and hydrogen; in any order.

In one embodiment, the at least one structural layer is a core, anintermediate layer or a cover, wherein the composition is disposed in atleast a portion of the at least one structural layer. The zincdimethacrylate may be present in an amount from about 0.01 pph to about100 pph and the at least one halogenated organosulfur compound offormula I is present in an amount from about 0.01 pph to about 50 pph.

In one embodiment, the at least one halogenated organosulfur compound offormula I is selected from the group consisting ofpentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol;4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol;3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol;3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol;2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol;pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol;4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol;3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol;3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol;2,3,5,6-tetrachlorothiophenol; pentabromothiophenol; 2-bromothiophenol;3-bromothiophenol; 4-bromothiophenol; 2,3-bromothiophenol;2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol;2,3,4-bromothiophenol; 3,4,5-bromothiophenol;2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol;pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol;4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol;3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol;3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenol; and their metal salts. In a preferredembodiment, the at least one halogenated organosulfur compound offormula I is a metal salt of Zn, Ca, Ba, Cd, Sn, Mg, and Mn. In anotherpreferred embodiment, the at least one halogenated organosulfur compoundof formula I is a metal salt of Zn. In yet another preferred embodiment,the at least one halogenated organosulfur compound of formula I is zincpentachlorothiophenol.

The free radical source may be di-tert-amyl peroxide,di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, or any mixture thereof.

In one embodiment, the composition further comprises one or moreadditional crosslinking agent selected from the group consisting of ametallic salt of an unsaturated acid monomer and a metallic salt of amonocarboxylic acid. In another embodiment, the cover comprises one ormore homopolymeric or copolymeric cover materials selected from thegroup consisting of thermoset polyurethane, thermoplastic polyurethane,thermoset polyurea, thermoplastic polyurea, thermoset elastomer,thermoplastic elastomer and thermoplastic ionomer.

In one embodiment, the golf ball core has an Atti compression of atleast about 40 and a coefficient of restitution of at least about 0.78.In another embodiment, the golf ball has a ball spin rate of about 2500rpm to about 4000 rpm when the golf ball is hit with a golf driver. Inyet another embodiment, the golf ball has a ball spin rate of about6,500 rpm to about 10,000 rpm when the golf ball is hit with an 8-iron.

In one embodiment, the flexural modulus of the intermediate layer isabout 2000 psi to about 200,000 psi and the flexural modulus of thecover is from about 5000 psi to about 100,000 psi. In anotherembodiment, the core has a hardness of about 15 Shore A or greater, theintermediate layer has a hardness of about 30 Shore D or greater, andthe cover has a hardness of 70 Shore D or less.

The resilient polymer component may be selected from the groupconsisting of a cis-polybutadiene, trans-polybutadiene,cis-polyisoprene, trans-polyisoprene, thermoplastic copolyesteresterblock copolymer; dynamically vulcanized thermoplastic elastomer;hydrogenated styrene-butadiene elastomer, non-hydrogenatedstyrene-butadiene elastomer; thermoplastic polyurethane; polymers madeusing a metallocene catalyst; ethylene propylenediene monomer; ethylenepropylene rubber; or mixtures thereof. In one embodiment, the resilientpolymer component comprises greater than 90% cis-polybutadiene. In stillanother embodiment, the resilient polymer component has a Mooneyviscosity from about 30 to about 120.

The present invention is also directed to a golf ball comprising atleast one structural layer formed from a composition that comprises aresilient polymer component, a free radical source, zinc dimethacrylateand zinc pentachlorothiophenol.

The present invention is also directed to a method of manufacturing golfballs comprising providing a core; optionally providing an intermediatelayer disposed outside the core; and providing at least one cover overthe core and optional intermediate layer, wherein at least one of thecover, the core, and the optional intermediate layer comprises at leastone layer formed from a composition that comprises a resilient polymercomponent, a free radical source, zinc dimethacrylate and at least onehalogenated organosulfur compound having the following general formulaI:

where R₁-R₅ can be substituted or unsubstituted C₁-C₈ alkyl groups;halogen groups; thiol groups (—SH), carboxylated groups; sulfonatedgroups; and hydrogen; in any order.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention can be ascertained fromthe following detailed description that is provided in connection withthe drawings described below:

FIG. 1 is a cross-sectional view of a two-piece golf ball having a coverand a core according to the invention;

FIG. 2 is a cross-section of a golf ball having an intermediate layerbetween a cover and a center according to the invention; and

FIG. 3 is a cross section of a golf ball having more than oneintermediate layer between a cover and a center according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to one-piece golf balls, two-piece golfballs, or multilayer golf balls having a center, at least oneintermediate layer disposed concentrically adjacent to the center, and acover. The invention also relates to golf balls having a double core, amulti-layer core, a double cover, a multi-layer cover or more than oneintermediate layer. At least one portion of the golf ball, i.e., one ofthe center, cover(s), or intermediate layer(s), includes a compositioncomprising zinc dimethacrylate (“ZDMA”) and at least one halogenatedorganosulfur compound having the following general formula I:

where R₁-R₅ can be substituted or unsubstituted C₁-C₈ alkyl groups;halogen groups; thiol groups (—SH), carboxylated groups; sulfonatedgroups; and hydrogen; in any order.

More particularly, at least one portion of the golf ball includes acomposition comprising a resilient polymer component; ZDMA; at least onehalogenated organosulfur compound of formula I and optionally a freeradical source. Without wishing to be bound by any theory, ZDMAfunctions as, inter alia, a crosslinker and the at least one halogenatedorganosulfur compound of formula I functions as, inter alia, avulcanization accelerator.

Typically, the addition of ZnPCTP to zinc diacrylate (“ZDA”) in corecompositions increases the TC90, lowers golf ball compression, andprovides a modest increase in the coefficient of restitution (“CoR,” asdefined below) at 125 feet per second, when compared to compositionscontaining ZDA but lacking ZnPCTP. In the present invention, theaddition of at least one of a halogenated organosulfur compound offormula I to ZDMA compositions surprisingly increases golf ballcompression, lowers the TC90, and provides significant increases in theCoR at 125 feet per second. The compositions of the present inventionalso provides golf balls having respectable CoR at 125 feet per second.

In one embodiment, ZDMA is present in an amount greater than about 10pph of the base polymer, preferably from about 0.01 pph to about 100pph, more preferably from about 1 pph to about 60 pph. As used herein,the term “parts per hundred”, also known as “pph”, is defined as thenumber of parts by weight of a particular component present in amixture, relative to 100 parts by weight of the total polymer component,which includes the resilient polymer component and any other polymercomponent. Mathematically, this can be expressed as the weight of aningredient divided by the total weight of the polymer, multiplied by afactor of 100. In another embodiment, ZDMA is present from about 5 pphto about 50 pph of base polymer, preferably from about 10 pph to about35 pph of base polymer, more preferably from about 15 to about 25 pph ofbase polymer.

Preferred halogenated organosulfur compounds having general formula Iinclude, but are not limited to, pentafluorothiophenol;2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol;2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol;3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their salts with Zn, Cd, Sn, Mg, andMn.

Preferably, the halogenated organosulfur compound ispentachlorothiophenol (“PCTP”), which is commercially available in neatform or under the tradename STRUKTOL®, a clay-based carrier containingthe sulfur compound pentachlorothiophenol loaded at 45 percent(correlating to 2.4 parts PCTP). STRUKTOL® is commercially availablefrom Struktol Company of America of Stow, Ohio. PCTP is commerciallyavailable in neat form from eChinachem of San Francisco, Calif. and inthe salt form from eChinachem of San Francisco, Calif. Most preferably,the halogenated organosulfur compound is the zinc salt ofpentachlorothiophenol (“ZnPCTP”), which is commercially available fromeChinachem of San Francisco, Calif.

As used herein, the term “substituted or unsubstituted C₁-C₈ alkyl”means any substituted or unsubstituted acyclic carbon-containing groupshaving from one to eight carbon atoms. Examples of substituted orunsubstituted C₁-C₈ alkyl groups include methyl, ethyl, propyl, butyl,pentyl, hexyl, and isomers thereof, including, for example, iso-propyl,iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, iso-pentyl,neo-pentyl, hexyl, heptyl, octyl, and the like). One of ordinary skillin the art is familiar with the various configurations of linear andbranched alkyl groups, which are within the scope of the presentinvention.

As used herein, the term “substituted” means groups that also containvarious substituents in which one or more hydrogen atoms is replaced bya functional group (e.g., a substituted alkyl group having one or morefunctional groups) or alkyl group as defined in the above. Functionalgroups include, but are not limited to, hydroxyl, amino (e.g., R₁R₂N,wherein R₁ and R₂ are each independently hydrogen, alkyl, aryl orcycloalkyl), alkoxy, carboxyl (e.g., ester, acid, and metal derivativesthereof), sulfoxidyl, sulfonyl, sulfonoyl, amido, phosphate, thiol,cyano, nitro, silyl and halogen (e.g., fluoro, chloro, bromo or iodo).

In one embodiment, the halogenated organosulfur compound of formula I ispresent in an amount from about 0.01 pph to about 50 pph, preferablyfrom about 0.1 pph to about 20 pph. In another embodiment, thehalogenated organosulfur compound of formula I is present in an amountfrom about 1 pph to about 5 pph, preferably from about 2 pph to about 3pph. The upper and lower limits of the ranges disclosed herein areinterchangeable to form new ranges. For example, the amount of thehalogenated organosulfur compound of formula I may be present from about0.1 pph to about 5 pph, from about 1 pph to about 3 pph, and even 5 pphto about 20 pph.

The compositions of the present invention may be used with any type ofball construction. For example, the ball may have a one-piece,two-piece, or three-piece design, a multi-layer core, a multi-layercover, one or more intermediate layers. As used herein, the term“multi-layer” means at least two layers, i.e., at least two structurallayers. For example, the compositions of the invention may be used in acore, intermediate layer, and/or cover of a golf ball, each of which mayhave a single layer or multiple layers. Thus, the invention encompassesgolf balls having at least one layer formed from a composition thatcomprises ZDMA and at least one halogenated organosulfur compound offormula I. As used herein, the term “layer” includes any generallyspherical portion of a golf ball, i.e., a golf ball core or center, anintermediate layer, and or a golf ball cover.

Thus, in one embodiment, a golf ball core comprises ZDMA and one or morehalogenated organosulfur compounds of formula I. In another embodiment,a golf ball having more than one layer in the core comprises ZDMA andone or more halogenated organosulfur compounds of formula I in at leastone of the core layers.

In another embodiment, a golf ball intermediate layer comprises ZDMA andone or more halogenated organosulfur compounds of formula I. In anotherembodiment, a golf ball having more than one intermediate layercomprises ZDMA and one or more halogenated organosulfur compounds offormula I in at least one of the intermediate layers.

In yet another embodiment, a golf ball cover comprises ZDMA and one ormore halogenated organosulfur compounds of formula I. In anotherembodiment, a golf ball having more than one cover comprises ZDMA andone or more halogenated organosulfur compounds of formula I in at leastone of the cover layers.

For example, FIG. 1 illustrates a golf ball according to the inventionwith a one-piece core. Golf ball 10 of the present invention can includea core 12 and a cover 16 surrounding the core 12, wherein at least oneof core 12 and cover 16 incorporates at least one layer comprising ZDMAand one or more halogenated organosulfur compounds of formula I.Similarly, FIG. 2 illustrates a multi-layer golf ball 20 that include acenter 22, a cover 26, and at least one intermediate layer 24 disposedbetween the cover and the center. Each of the cover and center may alsoinclude more than one layer; i.e., the golf ball can be a conventionalthree-piece wound ball, a two-piece ball, a ball having a multi-layercore or an intermediate layer or layers, etc. Thus, referring to FIG. 3,a golf ball 30 of the present invention can include a center 32, a cover38, and intermediate layers 34 and 36 disposed between the cover and thecenter. Although FIG. 3 shows only two intermediate layers, it will beappreciated that any number or type of intermediate layers may be used,as desired.

Resilient Polymer Component

The resilient polymer component includes natural or synthetic rubbers,as well as any combination thereof. Particular resilient polymercomponents include, but are not limited to, polybutadiene, includingcis-polybutadiene, trans-polybutadiene, or mixtures thereof; isoprene,including cis-polyisoprene, trans-polyisoprene, or mixtures thereof;thermoplastic copolyesterester block copolymer; dynamically vulcanizedthermoplastic elastomer; hydrogenated or non-hydrogenatedstyrene-butadiene elastomer; thermoplastic polyurethane; polymers madeusing a metallocene catalyst; ethylene propylenediene monomer; ethylenepropylene rubber; or mixtures thereof. In one embodiment, the resilientpolymer component is 1,4-polybutadiene having a cis-structure of atleast about 40 percent, of which natural rubber, polyisoprene rubberand/or styrene-butadiene rubber may be thereto. In another embodiment,the resilient polymer component is 1,4-polybutadiene having acis-structure of at least about 85% percent, preferably 90% and morepreferably 95%. In yet another embodiment, the resilient polymercomponent is from about 95% to about 99% cis-polybutadiene.

In one embodiment, the resilient polymer component has a Mooneyviscosity greater than about 20, preferably greater than about 30, andmore preferably greater than about 40. Mooney viscosity is typicallymeasured according to ASTM D-1646. In another embodiment, the Mooneyviscosity of the polybutadiene is greater than about 35, and preferablygreater than about 50. In one embodiment, the Mooney viscosity of thepolybutadiene is from about 40 to about 120. In yet another embodiment,the Mooney viscosity of the polybutadiene is from about 45 to about 60,more preferably from about 45 to about 55. As previously mentioned, theupper and lower limits of the ranges disclosed herein areinterchangeable to form new ranges. For example, the Mooney viscosity ofpolybutadiene may also be from about 45 to about 55, from about 40 toabout 45, and from about 55 to about 120.

Examples of desirable polybutadiene rubbers include BUNA® CB22 and BUNA®CB23, commercially available from Bayer of Akron, Ohio; UBEPOL® 360L andUBEPOL® 150L, commercially available from UBE Industries of Tokyo,Japan; and CARIFLEX® BCP820 and CARIFLEX® BCP824, and BR1220,commercially available from Dow Chemicals of Midland, Mich. If desired,the polybutadiene can also be mixed with other elastomers known in theart such as natural rubber, polyisoprene rubber and/or styrene-butadienerubber in order to modify the properties of the core.

Suitable thermoplastic copolyetheresters include HYTREL® 3078 andHYTREL® 4069, which are commercially available from E. I. DuPont deNemours & Co. of Wilmington, Del. Suitable dynamically vulcanizedthermoplastic elastomers include SANTOPRENE®, commercially availablefrom Advanced Elastomer Systems of Akron, Ohio. Examples of suitablefunctionalized styrene-butadiene elastomers, include KRATON FG-1901x andFG-1921x, which are available from the Shell Corporation of Houston,Tex. Examples of suitable thermoplastic polyurethanes include ESTANE®58133 and ESTANE® 58144, which are commercially available from the B.F.Goodrich Company of Cleveland, Ohio. Further, the materials for theintermediate layer described below may be in the form of a foamedpolymeric material. For example, suitable metallocene polymers includefoams of thermoplastic elastomers based on metallocenesingle-site-catalyst-based foams. Suitable thermoplastic polyetheramidesinclude PEBAX® 2533, PEBAX® 1205 and PEBAX® 4033 which are availablefrom Atofina of King of Prussia, Pa. Suitable thermoplastic ionomerresins include any number of olefinic based ionomers including SURLYN®and IOTEK®, which are commercially available from E. I. DuPont deNemours & Co. of Wilmington, Del., and Exxon Corporation of Irving,Tex., respectively. When the resilient polymer component includes anypolymers in addition to polybutadiene, polybutadiene will be present inat least 50 pph of the resilient polymer component, preferably in anamount greater than about 75 pph, and more preferably in an amountgreater than about 90 pph.

Free Radical Source

The free-radical source is typically a peroxide, and preferably anorganic peroxide, which decomposes during the cure cycle. Suitablefree-radical sources include organic peroxide compounds, such asdi-tert-amyl peroxide, di(2-tert-butyl-peroxyisopropyl)benzene peroxideor α,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and the like, and any mixturethereof.

Other examples include, but are not limited to, VAROX® 231XL and VAROX®DCP-R, commercially available from Atofina Chemicals, Inc. of King ofPrussia, Pa; PERKODOX® BC and PERKODOX® 14, commercially available fromAkzo Nobel of Chicago, Ill.; and ELASTOCHEM® DCP-70, commerciallyavailable from Rhein Chemie of Trenton, N.J.

The peroxide may be present in an amount greater than about 0.1 pph ofthe total resilient polymer component, preferably about 0.1 pph to about15 pph of the resilient polymer component.

Other Ingredients

Other materials conventionally included in golf ball compositions mayalso be added to the compositions of the invention. These additionalmaterials include, but are not limited to, density-adjusting fillers,reaction enhancers, crosslinking agents, optical brighteners, coloringagents, fluorescent agents, whitening agents, UV absorbers, hinderedamine light stabilizers, defoaming agents, processing aids, mica, talc,nano-fillers, and other conventional additives. Antioxidants,stabilizers, softening agents, plasticizers, including internal andexternal plasticizers, impact modifiers, foaming agents, excipients,reinforcing materials and compatibilizers may also be added to anycomposition of the invention. In addition, heat stabilizers may bebeneficial in enlarging the range of processing temperatures to greaterthan about 130° C. All of these materials, which are well known in theart, are added for their usual purpose in typical amounts.

Crosslinkers (i.e., crosslinking agents) in addition to ZDMA may beincluded to increase the hardness of the reaction product. Suitableadditional crosslinking agents include one or more metallic salts ofunsaturated acid monomers or unsaturated fatty acids having 3 to 8carbon atoms, such as acrylic or methacrylic acid, or monocarboxylicacids, including zinc, calcium, or magnesium acrylate salts, and thelike, and mixtures thereof. Exemplary additional crosslinkers include,but are not limited to, one or more metal salt diacrylates,dimethacrylates, and monomethacrylates, wherein the metal is magnesium,calcium, zinc, aluminum, sodium, lithium, or nickel. Preferred acrylatesinclude zinc acrylate, zinc diacrylate, zinc methacrylate, and mixturesthereof. Crosslinkers also include organic acids having more than onecarboxylic acid groups, including diacids, triacids and tetraacids.

The crosslinking agent must be present in an amount sufficient tocrosslink a portion of the chains of polymers in the resilient polymercomponent. For example, the desired compression may be obtained byadjusting the amount of crosslinking. This may be achieved, for example,by altering the type and amount of crosslinking agent, a methodwell-known to one of ordinary skill in the art. It is known that the useof crosslinkers increase the compression of golf balls.

The additional crosslinking agent may be present in an amount greaterthan about 0.1 percent of the polymer component, preferably from about 5to 40 percent of the resilient polymer component, more preferably fromabout 10 to 25 percent of the resilient polymer component.

In one embodiment, the additional crosslinking agent is present in anamount greater than about 10 pph of the base polymer, preferably fromabout 20 pph to about 40 pph of the base polymer, more preferably fromabout 25 pph to about 35 pph of the base polymer. The additionalcrosslinking agents can be in pure form, i.e., in 100% active form, ordispersed in a suitable carrier known to one of ordinary skill in theart.

In other embodiments, the golf ball further comprises a cis-to-transcatalyst, such as those described in copending U.S. application Ser Nos.10/437,386 and 10/437,387, the entirety of which are incorporated hereinby reference. Without being bound by any particular theory, it isbelieved that the cis-to-trans catalyst component, in conjunction with afree radical source, acts to convert a percentage of the polybutadienefrom the cis-to the trans-conformation. As used herein, “cis-to-transcatalyst” means any component or a combination thereof that will convertat least a portion of cis-isomer to trans-isomer at a given temperature.The cis-to-trans catalyst component may include one or more cis-to-transcatalysts described herein, but typically includes at least oneorganosulfur component (including metal-containing andnonmetal-containing organosulfur compounds), a Group VIA component, aninorganic sulfide, a substituted or unsubstituted aromatic organiccompound that does not contain sulfur or metal, an aromaticorganometallic compound, or any combination thereof. In one embodiment,the cis-to-trans catalyst is a blend of an organosulfur component and aninorganic sulfide component or a Group VIA component. In anotherembodiment, the cis-to-trans catalyst is a blend of an organosulfurcomponent, an inorganic sulfide component, and a Group VIA component. Inone embodiment, the halogenated organosulfur compound of formula Icatalyzes the cis-to-trans transformation of polybutadiene.

When elemental sulfur or polymeric sulfur is included in thecis-to-trans catalyst, an accelerator may be used to improve theperformance of the cis-to-trans catalyst and increase the trans-conversion for a given amount of sulfur catalyst. Suitable acceleratorsinclude, but are not limited to, sulfenamide, such as N-oxydiethylene2-benzothiazole-sulfenamide, thiazole, such as benzothiazyl disulfide,dithiocarbamate, such as bismuth dimethyldithiocarbamate, thiuram, suchas tetrabenzyl thiuram disulfide, xanthate, such as zinc isopropylxanthate, thiadiazine, thiourea, such as trimethylthiourea, guanadine,such as N,N′-di-ortho-tolylguanadine, or aldehyde-amine, such as abutyraldehyde-aniline condensation product, or mixtures thereof.

The cis-to-trans catalyst is typically present in an amount sufficientto produce a reaction product so as to increase the trans-polybutadieneisomer content to contain from about 5 percent to 70 percenttrans-isomer polybutadiene based on the total resilient polymercomponent. The cis-to-trans catalyst is preferably present in an amountfrom about 0.1 pph to 25 pph of the total amount of polybutadiene.

Core

The invention encompasses the use of ZDMA and one or more halogenatedorganosulfur compounds of formula I in a one-piece core or a multi-layercore. As used herein, the term “core” means the innermost portion of agolf ball, and may include one or more layers. When a multi-layer coreis contemplated, the core is the innermost component with one or moreadditional core layers disposed thereon. The present inventionencompasses compositions that could lead to better aging cores, as wellas more durable cores. In one embodiment, the one or more additionalcore layers are solid and includes a reinforcing polymer component asdescribed herein to improve the centering of the layers within the ball.

At least a portion of the core, typically the center, is solid,semi-solid, hollow, powder-filled or fluid-filled. As used herein, theterm “fluid” means a gas, liquid, gel, paste, or the like, or acombination thereof. Any core material known to one of ordinary skill inthe art also is suitable for use in the golf balls of the presentinvention.

In one embodiment, the core comprises ZDMA and one or more halogenatedorganosulfur compounds of formula I. The core may also includeconventional materials, for example, a resilient polymer component, afree radical source, an additional crosslinking agent, and a densityadjusting filler. Additional crosslinking agents include metal salts ofunsaturated fatty acids, such as zinc or magnesium salts of acrylic ormethacrylic acid. The density adjusting filler typically includesmaterials such as zinc oxide, barium sulfate, silica, calcium carbonate,zinc carbonate and the like, as well as foaming agents.

In one embodiment, the center composition comprises ZDMA and at leastone halogenated organosulfur compound of formula I, and a resilientpolymer component having a resilience index of at least about 40. Inanother embodiment, the resilience index of the resilient polymercomponent is at least about 50.

The ZDMA, at least one halogenated organosulfur compound of formula I,resilient polymer component, free-radical initiator, filler(s), and anyother materials used in forming either the golf ball center or anyportion of the core, in accordance with invention, may be combined toform a polymer mixture by any type of mixing known to one of ordinaryskill in the art.

The compression of the core, or portion of the core, of golf ballsprepared according to the invention is typically below 100, preferablybelow about 90, more preferably below about 80. In one embodiment, thecompression of the core, or portion of the core, of golf balls is fromabout 25 to about 100. In another embodiment, the compression of thecore, or portion of the core, of golf balls is from about 50 to about95. In yet another embodiment, the compression of the core, or portionof the core, of golf balls is from about 75 to about 90.

The compositions of the present invention preferably have a hardness ofat least about 15 Shore A, more preferably between about 30 Shore A and80 Shore D, and even more preferably between about 50 Shore A and 60Shore D. In addition, the specific gravity is typically greater thanabout 0.7, preferably greater than about 1, for the golf ballpolybutadiene material. Moreover, the reaction product preferably has aflexural modulus of from about 500 psi to about 300,000 psi, preferablyfrom about 1,000 to about 250,000, and more preferably from about 2,000to about 200,000 psi.

Although the compositions discussed herein relate to core compositions,the invention also encompasses the use of such compositions to form atleast a portion of any component of a golf ball, including the cover(s)and intermediate layer(s).

Fillers added to one or more portions of the golf ball typically includeprocessing aids or compounds to affect Theological and mixingproperties, the specific gravity (i.e., density-modifying fillers), themodulus, the tear strength, reinforcement, and the like. The fillers aregenerally inorganic, and suitable fillers include numerous metals(including metal powders) or metal oxides, such as zinc oxide and tinoxide, as well as barium sulfate, zinc sulfate, calcium carbonate,barium carbonate, clay, tungsten, tungsten carbide, an array of silicas,and mixtures thereof. Fillers may also include various foaming agents orblowing agents which may be readily selected by one of ordinary skill inthe art. Foamed polymer blends may be formed by blending ceramic orglass microspheres with polymer material. Polymeric, ceramic, metal, andglass microspheres may be solid or hollow, and filled or unfilled.Fillers are typically also added to one or more portions of the golfball to modify the density thereof to conform to uniform golf ballstandards. Fillers may also be used to modify the weight of the centeror at least one additional layer for specialty balls, e.g., a lowerweight ball is preferred for a player having a low swing speed.

Intermediate Layer

An “intermediate layer” (also known as inner layer or mantle layer) isdefined herein as a portion of the golf ball that occupies a volumebetween the cover and the core. Such an intermediate layer may bedistinguished from a cover or a core by some difference between the golfball layers, e.g., hardness, compression, thickness, and the like. Anintermediate layer may be used, if desired, with a multilayer cover or amultilayer core, or with both a multilayer cover and a multilayer core.Accordingly, an intermediate layer is also sometimes referred to in theart as an inner cover layer, as an outer core layer or as a mantlelayer, i.e., any layer(s) disposed between the inner core and the outercover of a golf ball, this layer may be incorporated, for example, witha single layer or a multilayer cover, with a one-piece core or amultilayer core, with both a single layer cover and core, or with both amultilayer cover and a multilayer core. As with the core, theintermediate layer may also include a plurality of layers. It will beappreciated that any number or type of intermediate layers may be used,as desired.

When the golf ball of the present invention includes an intermediatelayer, such as an inner cover layer or outer core layer, i.e., anylayer(s) disposed between the inner core and the outer cover of a golfball, the intermediate layer can include at least one layer thatcomprises a composition that includes a resilient polymer component; afree radical source; ZDMA, and at least one halogenated organosulfurcompound of formula I, as described hereinabove. In another embodiment,the intermediate layer can further include any materials known to one ofordinary skill in the art including thermoplastic and thermosettingmaterials.

The intermediate layer also likewise may include one or morehomopolymeric or copolymeric materials, such as vinyl resins,polyolefins, polyurethanes, and polyureas, such as the ones disclosed inU.S. Pat. Nos. 5,334,673, and 5,484,870, polyamides, acrylic resins,thermoplastics, polyphenylene oxide resins, thermoplastic polyesters,blends and alloys, blends of thermoplastic rubbers, such as thosedisclosed in U.S. Pat. No. 6,162,135, the entirety of which isincorporated herein by reference.

In another embodiment, the intermediate layer includes polymers, such asethylene, propylene, butene-1 or hexane-1 based homopolymers orcopolymers including functional monomers, such as acrylic andmethacrylic acid and fully or partially neutralized ionomer resins andtheir blends, methyl acrylate, methyl methacrylate homopolymers andcopolymers, imidized, amino group containing polymers, polycarbonate,reinforced polyamides, polyphenylene oxide, high impact polystyrene,polyether ketone, polysulfone, poly(phenylene sulfide),acrylonitrile-butadiene, acrylic-styrene-acrylonitrile, poly(ethyleneterephthalate), poly(butylene terephthalate), poly(ethylene vinylalcohol), poly(tetrafluoroethylene) and their copolymers includingfunctional comonomers, and blends thereof.

An intermediate layer may include ionomeric materials, such as ioniccopolymers of ethylene and an unsaturated monocarboxylic acid, which areavailable under the trademark SURLYN® of E. I. DuPont de Nemours & Co.,of Wilmington, Del., or IOTEK® or ESCOR® of Exxon.

The intermediate layer may also include at least one ionomer, such asacid-containing ethylene copolymer ionomers, including E/X/Y terpolymerswhere E is ethylene, X is an acrylate or methacrylate-based softeningcomonomer present in about 0 to 50 weight percent and Y is acrylic ormethacrylic acid present in about 5 to 35 weight percent. The ionomeralso may include so-called “low acid” and “high acid” ionomers, as wellas blends thereof, such as those disclosed in copending U.S. applicationSer. Nos. 10/437,386 and 10/437,387, the entirety of which isincorporated herein by reference. In general, ionic copolymers includingup to about 15 percent acid are considered “low acid” ionomers, whilethose including greater than about 15 percent acid are considered “highacid” ionomers.

In one embodiment, the intermediate layer may be formed from at leastone polymer containing α,β-unsaturated carboxylic acid groups, or thesalts thereof, that have been 100 percent neutralized by organic fattyacids, such as those disclosed in copending U.S. application Ser. Nos.10/437,386 and 10/437,387, the entirety of which is incorporated hereinby reference.

In another embodiment, the intermediate layer may also be formed fromhighly neutralized polymers, such as those disclosed U.S. PatentPublication No. 2001/0018375 and 2001/0019971, the entirety of which areincorporated herein by reference; and/or grafted and non-graftedmetallocene catalyzed polyolefins and polyamides, polyamide/ionomerblends, and polyamide/nonionomer blends, such as those disclosed in U.S.patent application Ser. No. 10/138,304, filed May 6, 2002, entitled“Golf Ball Incorporating Grafted Metallocene Catalyzed Polymer Blends,”which is incorporated by reference herein in its entirety; among otherpolymers. Examples of other suitable intermediate layer materialsinclude blends of some of the above materials, such as those disclosedin U.S. Pat. No. 5,688,181, the entire disclosure of which isincorporated by reference herein.

In another embodiment, the intermediate layer includes at least oneprimarily or fully non-ionomeric thermoplastic material. Suitablenon-ionomeric materials include polyamides and polyamide blends, graftedand non-grafted metallocene catalyzed polyolefins or polyamides,polyamide/ionomer blends, polyamide/nonionomer blends, polyphenyleneether/ionomer blends, and mixtures thereof.

The intermediate layer may include a resilient polymer component, whichis preferably used as the majority polymer in the intermediate layer toimpart resilience in the cured state, and a reinforcing polymercomponent as a blend. Examples of such materials are disclosedhereinabove.

The resilient polymer component, reinforcing polymer component,free-radical initiator, and any other materials used in forming anintermediate layer of a golf ball core in accordance with invention maybe combined by any type of mixing known to one of ordinary skill in theart.

The intermediate layer may also be formed from the compositions asdisclosed in U.S. Pat. No. 5,688,191, the entire disclosure of which isincorporated by reference herein.

The intermediate layer may also be a tensioned elastomeric materialwound around a solid, semi-solid, hollow, fluid-filled, or powder-filledcenter. A wound layer may be described as a core layer or anintermediate layer for the purposes of the invention. As an example, thegolf ball may include a core layer, a tensioned elastomeric layer woundthereon, and a cover layer. In particular, the golf ball may have a coremade of a composition containing ZDMA and at least one halogenatedorganosulfur compound of formula I, an intermediate layer including atensioned elastomeric material and a cover. The tensioned elastomericmaterial may be formed of any suitable material known to one of ordinaryskill in the art.

In one embodiment, the tensioned elastomeric material incorporates thereaction product discussed above. The tensioned elastomeric material mayalso be formed conventional polyisoprene.

In one embodiment, the tensioned elastomeric layer is a high tensilefilament having a tensile modulus of about 10,000 kpsi or greater, asdisclosed in co-pending U.S. patent application Ser. No. 09/842,829,filed Apr. 27, 2001, entitled “All Rubber Golf Ball with Hoop-StressLayer,” the entire disclosure of which is incorporated by referenceherein. In another embodiment, the tensioned elastomeric layer is coatedwith a binding material that will adhere to the core and itself whenactivated, causing the strands of the tensioned elastomeric layer toswell and increase the cross-sectional area of the layer by at leastabout 5 percent. An example of such a golf ball construction is providedin co-pending U.S. patent application Ser. No. 09/841,910, the entiredisclosure of which is incorporated by reference herein.

The intermediate layer may also be formed of a binding material and aninterstitial material distributed in the binding material, wherein theeffective material properties of the intermediate layer are uniquelydifferent for applied forces normal to the surface of the ball fromapplied forces tangential to the surface of the ball. Examples of thistype of intermediate layer are disclosed in U.S. patent application Ser.No. 10/028,826, filed Dec. 28, 2001, entitled, “Golf Ball with aRadially Oriented Transversely Isotropic Layer and Manufacture of Same,”the entire disclosure of which is incorporated by reference herein. Inone embodiment of the present invention, the interstitial material mayextend from the intermediate layer into the core. In an alternativeembodiment, the interstitial material can also be embedded in the cover,or be in contact with the inner surface of the cover, or be embeddedonly in the cover.

At least one intermediate layer may also be a moisture barrier layer,such as the ones described in U.S. Pat. No. 5,820,488, which isincorporated by reference herein. Any suitable film-forming materialhaving a lower water vapor transmission rate than the other layersbetween the core and the outer surface of the ball, i.e., cover, primer,and clear coat. Examples include, but are not limited to polyvinylidenechloride, vermiculite, and a reaction product with fluorine gas. In oneembodiment, the moisture barrier layer has a water vapor transmissionrate that is sufficiently low to reduce the loss of CoR of the golf ballby at least 5 percent if the ball is stored at 100° F. and 70 percentrelative humidity for six weeks as compared to the loss in CoR of a golfball that does not include the moisture barrier, has the same type ofcore and cover, and is stored under substantially identical conditions.

Additional materials may be included in the intermediate layercompositions outlined above. For example, catalysts, coloring agents,optical brighteners, crosslinking agents, whitening agents such as TiO₂and ZnO, UV absorbers, hindered amine light stabilizers, defoamingagents, processing aids, surfactants, and other conventional additivesmay be added to the intermediate layer compositions of the invention. Inaddition, antioxidants, stabilizers, softening agents, plasticizers,including internal and external plasticizers, impact modifiers, foamingagents, density-adjusting fillers, reinforcing materials, andcompatibilizers may also be added to any of the intermediate layercompositions. One of ordinary skill in the art should be aware of therequisite amount for each type of additive to realize the benefits ofthat particular additive.

Cover

The cover provides the interface between the ball and a club. Propertiesthat are desirable for the cover are good moldability, high abrasionresistance, high tear strength, high resilience, and good mold release,among others.

As used herein, the term “cover” means the outermost portion of a golfball. A cover typically includes at least one layer and may containindentations such as dimples and/or ridges. Paints and/or laminates aretypically disposed about the cover to protect the golf ball during usethereof.

Prior to forming the cover layer, the inner ball, i.e., the core and anyintermediate layers disposed thereon, may be surface treated to increasethe adhesion between the outer surface of the inner ball and the cover.Examples of such surface treatment may include mechanically orchemically abrading the outer surface of the subassembly. Additionally,the inner ball may be subjected to corona discharge or plasma treatmentprior to forming the cover around it. Other layers of the ball, e.g.,the core, also may be surface treated. Examples of these and othersurface treatment techniques can be found in U.S. Pat. No. 6,315,915,the entirety of which is incorporated by reference herein.

In one embodiment, the cover is formed from a composition that includesa resilient polymer component; a free radical source; ZDMA, and at leastone halogenated organosulfur compound of formula I.

The cover may also likewise include one or more homopolymeric orcopolymeric materials, such as vinyl resins, polyolefins, polyurethanes,and polyureas, such as the ones disclosed in U.S. Pat. Nos. 5,334,673,and 5,484,870, polyamides, acrylic resins, thermoplastics, polyphenyleneoxide resins, thermoplastic polyesters, blends and alloys, blends ofthermoplastic rubbers, such as those disclosed in U.S. Pat. No.6,162,135, the entirety of which is incorporated herein by reference.

In one embodiment, the cover includes one or more homopolymeric orcopolymeric cover materials, including but not limited to, thermosetpolyurethane, thermoplastic polyurethane, thermoset polyurea,thermoplastic polyurea, thermoset elastomer, thermoplastic elastomer orthermoplastic ionomer. In another embodiment, the cover includes one ormore homopolymeric or copolymeric cover materials that is light stable.

Preferably, the cover includes polymers, such as ethylene, propylene,butene-1 or hexane-1 based homopolymers or copolymers includingfunctional monomers, such as acrylic and methacrylic acid and fully orpartially neutralized ionomer resins and their blends, methyl acrylate,methyl methacrylate homopolymers and copolymers, imidized, amino groupcontaining polymers, polycarbonate, reinforced polyamides, polyphenyleneoxide, high impact polystyrene, polyether ketone, polysulfone,poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethylene vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers, and blends thereof. Suitable cover compositions also includea polyether or polyester thermoplastic urethane, a thermosetpolyurethane, a low modulus ionomer, such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present inabout 0 to 50 weight percent and Y is acrylic or methacrylic acidpresent in about 5 to 35 weight percent. More preferably, in a low spinrate embodiment designed for maximum distance, the acrylic ormethacrylic acid is present in about 15 to 35 weight percent, making theionomer a high modulus ionomer. In a high spin embodiment, the coverincludes an ionomer where an acid is present in about 10 to 15 weightpercent and includes a softening comonomer.

In another embodiment, the cover material is formed from polyurea, whichis disclosed in co-pending U.S. patent application Ser. Nos. 10/238,729,10/256,011, 10/066,637 and 10/228,311, the entire disclosures of whichare incorporated herein by reference.

In one embodiment, an intermediate cover layer may be formed from atleast one polymer containing α,β-unsaturated carboxylic acid groups, orthe salts thereof, that have been 100 percent neutralized by organicfatty acids. The organic acids are aliphatic, mono-functional(saturated, unsaturated, or multi-unsaturated) organic acids. Salts ofthese organic acids may also be used, including salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium; as well as salts of fatty acids, particularlystearic, behenic, erucic, oleic, or linoelic acids or dimerizedderivatives thereof. It is preferred that the organic acids and salts ofthe present invention be relatively non-migratory (i.e., they do notbloom to the surface of the polymer under ambient temperatures) andnon-volatile (they do not volatilize at temperatures required formelt-blending).

In another embodiment, the cover may also be formed from highlyneutralized polymers, such as those disclosed U.S. Patent PublicationNo. 2001/0018375 and 2001/0019971, the entirety of which areincorporated herein by reference; and/or grafted and non-graftedmetallocene catalyzed polyolefins and polyamides, polyamide/ionomerblends, and polyamide/nonionomer blends, such as those disclosed in U.S.patent application Ser. No. 10/138,304, filed May 6, 2002, entitled“Golf Ball Incorporating Grafted Metallocene Catalyzed Polymer Blends,”which is incorporated by reference herein in its entirety; among otherpolymers.

The cover of the golf balls typically has a thickness of at least about0.03 inches, preferably 0.03 to 0.125 inches, and more preferably fromabout 0.05 to 0.1 inches. The golf balls also typically have at leastabout 60 percent dimple coverage, preferably at least about 70 percentdimple coverage, of the surface area of the cover.

Typically, the covers are formed around the solid or wound cores bycompression molding preformed half-shells of the cover stock material,casting, or injection molding the cover stock about the core, includingreaction injection molding and liquid injection molding (“LIM”).Half-shells are made by injection molding a cover stock into aconventional half-shell mold in a conventional manner. The preferredmethod is compression molding of preformed half-shells.

The cover may include a plurality of layers, e.g., an inner cover layerdisposed about a golf ball center and an outer cover layer formedthereon. For example, the present invention encompasses a golf ballhaving a core, a thin inner cover layer, and a thin outer cover layerdisposed thereon.

In another embodiment, the outer cover layer has a different hardnessthan the inner cover layer. In one embodiment, the inner cover layer hasa hardness from about 30 Shore D to about 75 Shore D. In anotherembodiment, the inner cover layer has a hardness from about 40 Shore Dto about 70 Shore D. In yet another embodiment, the inner cover layerhas a hardness from about 50 Shore D to about 60 Shore D. In oneembodiment, the outer cover layer has a hardness from about 25 Shore Dto about 65 Shore D. In another embodiment, the outer cover layer has ahardness from about 40 Shore D to about 60 Shore D. In yet anotherembodiment, the outer cover layer has a hardness from about 45 Shore Dto about 55 Shore D.

In one embodiment, the difference in hardness of the outer cover layerand the inner cover layer is from about 5 Shore D to about 50 Shore D.In another embodiment, the difference in hardness of the outer coverlayer and the inner cover layer is from about 10 Shore D to about 30Shore D. In yet another embodiment, the difference in hardness of theouter cover layer and the inner cover layer is from about 15 Shore D toabout 20 Shore D. Depending on the desired performance and field, thehardness of the inner cover layer may be greater than the hardness ofthe outer cover layer, or the hardness of the inner cover layer may beless than the hardness of the outer cover layer.

While hardness gradients are typically used in a golf ball to achievecertain characteristics, the present invention also contemplates thecompositions of the invention being used in a golf ball with multiplecover layers having essentially the same hardness, wherein at least oneof the layers has been modified in some way to alter a property thataffects the performance of the ball. Such ball constructions aredisclosed in co-pending U.S. patent application Ser. No. 10/167,744,filed Jun. 13, 2002, entitled “Golf Ball with Multiple Cover Layers,”the entire disclosure of which is incorporated by reference herein.

In one such embodiment, both covers layers can be formed of the samematerial and have essentially the same hardness, but the layers aredesigned to have different coefficient of friction values. In anotherembodiment, the compositions of the invention are used in a golf ballwith multiple cover layers having essentially the same hardness, butdifferent rheological properties under high deformation. Another aspectof this embodiment relates to a golf ball with multiple cover layershaving essentially the same hardness, but different thicknesses tosimulate a soft outer cover over hard inner cover ball.

Other non-limiting examples of suitable types of ball constructions thatmay be used with the present invention include those described in U.S.Pat. Nos. 6,056,842, 5,688,191, 5,713,801, 5,803,831, 5,885,172,5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, as well as inPublication Nos. US2001/0009310 A1, US2002/0025862, and US2002/0028885.The entire disclosures of these patents and published patentapplications are incorporated by reference herein.

Methods of Forming Layers

The golf balls of the invention may be formed using a variety ofapplication techniques such as compression molding, flip molding,injection molding, retractable pin injection molding, reaction injectionmolding (RIM), liquid injection molding (LIM), casting, vacuum forming,powder coating, flow coating, spin coating, dipping, spraying, and thelike. A method of injection molding using a split vent pin can be foundin co-pending U.S. patent application Ser. No. 09/742,435, filed Dec.22, 2000, entitled “Split Vent Pin for Injection Molding.” Examples ofretractable pin injection molding may be found in U.S. Pat. Nos.6,129,881, 6,235,230, and 6,379,138. These molding references areincorporated in their entirety by reference herein. In addition, achilled chamber, i.e., a cooling jacket, such as the one disclosed inU.S. patent application Ser. No. 09/717,136, filed Nov. 22, 2000,entitled “Method of Making Golf Balls” may be used to cool thecompositions of the invention when casting, which also allows for ahigher loading of catalyst into the system.

Conventionally, compression molding and injection molding are applied tothermoplastic materials, whereas RIM, liquid injection molding, andcasting are employed on thermoset materials. These and other manufacturemethods are disclosed in U.S. Pat. Nos. 5,334,673, 5,484,870, and5,733,428, the disclosures of which are incorporated herein by referencein their entirety.

Forming the Core Layer(s)

The cores of the invention may be formed by any suitable method known toone of ordinary skill in art. When the cores are formed from a thermosetmaterial, compression molded is a particularly suitable method offorming the core. In a thermoplastic core embodiment, on the other hand,the cores may be injection molded.

Suitable methods include single pass mixing (ingredients are addedsequentially), multi-pass mixing, and the like. The crosslinking agent,and any other optional additives used to modify the characteristics ofthe golf ball center or additional layer(s), may similarly be combinedby any type of mixing. Suitable mixing equipment is well known to one ofordinary skill in the art, and such equipment may include a Banburymixer, a two-roll mill, or a twin screw extruder. Suitable mixing speedsand temperatures are well-known to one of ordinary skill in the art, ormay be readily determined without undue experimentation.

The mixture can be subjected to, e.g., a compression or injectionmolding process, and the molding cycle may have a single step of moldingthe mixture at a single temperature for a fixed-time duration. In oneembodiment, a single-step cure cycle is employed. Although the curingtime depends on the various materials selected, a suitable curing timeis about 5 minutes to about 18 minutes, preferably from about 8 minutesto about 15 minutes, and more preferably from about 10 minutes to about12 minutes. An example of a single step molding cycle, for a mixturethat contains dicumyl peroxide, would hold the polymer mixture at 171°C. (340° F.) for a duration of 15 minutes. An example of a two-stepmolding cycle would be holding the mold at 143° C. (290° F.) for 40minutes, then ramping the mold to 171° C. (340° F.) where it is held fora duration of 20 minutes. One of ordinary skill in the art will bereadily able to adjust the curing time based on the particular materialsused and the discussion herein.

Furthermore, U.S. Pat. Nos. 6,180,040 and 6,180,722 disclose methods ofpreparing dual core golf balls. The entire disclosures of these patentsare hereby incorporated by reference herein.

Forming the Intermediate Layer(s)

The intermediate layer may also be formed from using any suitable methodknown to one of ordinary skill in the art. For example, an intermediatelayer may be formed by blow molding and covered with a dimpled coverlayer formed by injection molding, compression molding, casting, vacuumforming, powder coating, and the like.

For example, castable reactive liquid materials, such as the reactionproducts of the invention may be applied over the inner ball using avariety of application techniques such as spraying, compression molding,dipping, spin coating, or flow coating methods that are well known inthe art. In one embodiment, the castable reactive reaction product isformed over the core using a combination of casting and compressionmolding. Conventionally, compression molding and injection molding areapplied to thermoplastic cover materials, whereas RIM, liquid injectionmolding, and casting are utilized on thermoset cover techniques.

Forming the Cover Layer(s)

The compositions of the invention may be applied over an inner ballusing a variety of application techniques such as spraying, compressionmolding, dipping, spin coating, or flow coating methods that are wellknown in the art. In one embodiment, the compositions of the inventionare used to form a cover over the core using a combination of castingand compression molding. Conventionally, compression molding andinjection molding are applied to thermoplastic cover materials, whereasRIM, liquid injection molding, and casting are employed on thermosetcover materials.

In addition, when covers for the golf balls of the invention are formedof polyurea and/or polyurethane compositions, these materials may beapplied over an inner ball using a variety of application techniquessuch as spraying, compression molding, dipping, spin coating, casting,or flow coating methods that are well known in the art. Examples offorming polyurea and polyurethane materials about an inner ball aredisclosed in U.S. Pat. Nos. 6,207,784, 5,733,428, 5,006,297, and5,334,673, which are incorporated by reference in their entirety herein.In one embodiment, a combination of casting and compression molding canbe used to form a polyurethane or polyurea composition over an innerball. However, the method of forming covers according to the inventionis not limited to the use of these techniques; other methods known tothose skilled in the art may also be employed.

Dimples

The use of various dimple patterns and profiles provides a relativelyeffective way to modify the aerodynamic characteristics of a golf ball.As such, the manner in which the dimples are arranged on the surface ofthe ball can be by any available method. For instance, the ball may havean icosahedron-based pattern, such as described in U.S. Pat. No.4,560,168, or an octahedral-based dimple patterns as described in U.S.Pat. No. 4,960,281.

In one embodiment of the present invention, the golf ball has anicosahedron dimple pattern that includes 20 triangles made from about362 dimples and, except perhaps for the mold parting line, does not havea great circle that does not intersect any dimples. Each of the largetriangles, preferably, has an odd number of dimples (7) along each sideand the small triangles have an even number of dimples (4) along eachside. To properly pack the dimples, the large triangle has nine moredimples than the small triangle. In another embodiment, the ball hasfive different sizes of dimples in total. The sides of the largetriangle have four different sizes of dimples and the small triangleshave two different sizes of dimples.

In another embodiment of the present invention, the golf ball has anicosahedron dimple pattern with a large triangle including threedifferent dimples and the small triangles having only one diameter ofdimple. In a preferred embodiment, there are 392 dimples and one greatcircle that does not intersect any dimples. In another embodiment, morethan five alternative dimple diameters are used.

In one embodiment of the present invention, the golf ball has anoctahedron dimple pattern including eight triangles made from about 440dimples and three great circles that do not intersect any dimples. Inthe octahedron pattern, the pattern includes a third set of dimplesformed in a smallest triangle inside of and adjacent to the smalltriangle. To properly pack the dimples, the large triangle has nine moredimples than the small triangle and the small triangle has nine moredimples than the smallest triangle. In this embodiment, the ball has sixdifferent dimple diameters distributed over the surface of the ball. Thelarge triangle has five different dimple diameters, the small trianglehas three different dimple diameters and the smallest triangle has twodifferent dimple diameters.

Alternatively, the dimple pattern can be arranged according tophyllotactic patterns, such as described in U.S. Pat. No. 6,338,684,which is incorporated herein in its entirety.

Dimple patterns may also be based on Archimedean patterns including atruncated octahedron, a great rhombcuboctahedron, a truncateddodecahedron, and a great rhombicosidodecahedron, wherein the patternhas a non-linear parting line, as disclosed in U.S. patent applicationSer. No. 10/078,417, which is incorporated by reference herein.

The golf balls of the present invention may also be covered withnon-circular shaped dimples, i.e., amorphous shaped dimples, asdisclosed in U.S. Pat. No. 6,409,615, which is incorporated in itsentirety by reference herein.

Dimple patterns that provide a high percentage of surface coverage arepreferred, and are well known in the art. For example, U.S. Pat. Nos.5,562,552, 5,575,477, 5,957,787, 5,249,804, and 4,925,193 disclosegeometric patterns for positioning dimples on a golf ball. In oneembodiment, the golf balls of the invention have a dimple coverage ofthe surface area of the cover of at least about 60 percent, preferablyat least about 65 percent, and more preferably at least 70 percent orgreater. Dimple patterns having even higher dimple coverage values mayalso be used with the present invention. Thus, the golf balls of thepresent invention may have a dimple coverage of at least about 75percent or greater, about 80 percent or greater, or even about 85percent or greater.

In addition, a tubular lattice pattern, such as the one disclosed inU.S. Pat. No. 6,290,615, which is incorporated by reference in itsentirety herein, may also be used with golf balls of the presentinvention. The golf balls of the present invention may also have aplurality of pyramidal projections disposed on the intermediate layer ofthe ball, as disclosed in U.S. Pat. No. 6,383,092, which is incorporatedin its entirety by reference herein. The plurality of pyramidalprojections on the golf ball may cover between about 20 percent to about80 of the surface of-the intermediate layer.

In an alternative embodiment, the golf ball may have a non-planarparting line allowing for some of the plurality of pyramidal projectionsto be disposed about the equator. Such a golf ball may be fabricatedusing a mold as disclosed in co-pending U.S. patent application Ser. No.09/442,845, filed Nov. 18, 1999, entitled “Mold For A Golf Ball,” andwhich is incorporated in its entirety by reference herein. Thisembodiment allows for greater uniformity of the pyramidal projections.

Several additional non-limiting examples of dimple patterns with varyingsizes of dimples are also provided in U.S. Pat. No. 6,358,161 and U.S.Pat. No. 6,213,898, the entire disclosures of which are incorporated byreference herein.

The total number of dimples on the ball, or dimple count, may varydepending on such factors as the dimple size and the selected pattern.In general, the total number of dimples on the ball preferably isbetween about 100 to about 1000 dimples, although one skilled in the artwould recognize that differing dimple counts within this range cansignificantly alter the flight performance of the ball. In oneembodiment, the dimple count is about 380 dimples or greater, but morepreferably is about 400 dimples or greater, and even more preferably isabout 420 dimples or greater. In one embodiment, the dimple count on theball is about 422 dimples. In some cases, it may be desirable to havefewer dimples on the ball. Thus, one embodiment of the present inventionhas a dimple count of about 380 dimples or less, and more preferably isabout 350 dimples or less.

Dimple profiles revolving a catenary curve about its symmetrical axismay increase aerodynamic efficiency, provide a convenient way to alterthe dimples to adjust ball performance without changing the dimplepattern, and result in uniformly increased flight distance for golfersof all swing speeds. Thus, catenary curve dimple profiles, as disclosedin U.S. patent application Ser. No. 09/989,191, filed Nov. 21, 2001,entitled “Golf Ball Dimples with a Catenary Curve Profile,” which isincorporated in its entirety by reference herein, is contemplated foruse with the golf balls of the present invention.

Golf Ball Post-Processing

The golf balls of the present invention may be painted, coated, orsurface treated for further benefits.

For example, golf balls covers frequently contain a fluorescent materialand/or a dye or pigment to achieve the desired color characteristics. Agolf ball of the invention may also be treated with a base resin paintcomposition, however, as disclosed in U.S. Patent Publication No.2002/0082358, which includes a 7-triazinylamino-3-phenylcoumarinderivative as the fluorescent whitening agent to provide improvedweather resistance and brightness.

In addition, trademarks or other indicia may be stamped, i.e.,pad-printed, on the outer surface of the ball cover, and the stampedouter surface is then treated with at least one clear coat to give theball a glossy finish and protect the indicia stamped on the cover.

The golf balls of the invention may also be subjected to dyesublimation, wherein at least one golf ball component is subjected to atleast one sublimating ink that migrates at a depth into the outersurface and forms an indicia. The at least one sublimating inkpreferably includes at least one of an azo dye, a nitroarylamine dye, oran anthraquinone dye. U.S. patent application Ser. No. 10/012,538, filedDec. 12, 2001, entitled, “Method of Forming Indicia on a Golf Ball,” theentire disclosure of which is incorporated by reference herein.

Laser marking of a selected surface portion of a golf ball causing thelaser light-irradiated portion to change color is also contemplated foruse with the present invention. U.S. Pat. Nos. 5,248,878 and 6,075,223generally disclose such methods, the entire disclosures of which areincorporated by reference herein. In addition, the golf balls may besubjected to ablation, i.e., directing a beam of laser radiation onto aportion of the cover, irradiating the cover portion, wherein theirradiated cover portion is ablated to form a detectable mark, whereinno significant discoloration of the cover portion results therefrom.Ablation is discussed in U.S. Pat. No. 6,462,303, the entirety of whichis incorporated by reference herein.

Protective and decorative coating materials, as well as methods ofapplying such materials to the surface of a golf ball cover, are wellknown in the golf ball art. Generally, such coating materials includeurethanes, urethane hybrids, epoxies, polyesters and acrylics. Ifdesired, more than one coating layer can be used. The coating layer(s)may be applied by any suitable method known to one of ordinary skill inthe art. In one embodiment, the coating layer(s) is applied to the golfball cover by an in-mold coating process, such as described in U.S. Pat.No. 5,849,168, which is incorporated in its entirety by referenceherein.

Golf Ball Properties

The properties such as hardness, modulus, core diameter, intermediatelayer thickness and cover layer thickness of the golf balls of thepresent invention have been found to effect play characteristics such asspin, initial velocity and feel of the present golf balls. For example,the flexural and/or tensile modulus of the intermediate layer arebelieved to have an effect on the “feel” of the golf balls of thepresent invention.

Component Dimensions

Dimensions of golf ball components, i.e., thickness and diameter, mayvary depending on the desired properties. For the purposes of theinvention, any layer thickness may be employed. Non-limiting examples ofthe various embodiments outlined above are provided here with respect tolayer dimensions.

The present invention relates to golf balls of any size. While “TheRules of Golf” by the USGA dictate specifications that limit the size ofa competition golf ball to more than 1.680 inches in diameter, golfballs of any size can be used for leisure golf play. The preferreddiameter of the golf balls is from about 1.680 inches to about 1.800inches. The more preferred diameter is from about 1.680 inches to about1.760 inches. A diameter of from about 1.680 inches to about 1.740inches is most preferred, however diameters anywhere in the range offrom 1.700 to about 1.950 inches can be used. Preferably, the overalldiameter of the core and all intermediate layers is about 80 percent toabout 98 percent of the overall diameter of the finished ball.

The core may have a diameter ranging from about 0.090 inches to about1.650 inches. In one embodiment, the diameter of the core of the presentinvention is about 1.200 inches to about 1.630 inches. In anotherembodiment, the diameter of the core is about 1.300 inches to about1.600 inches, preferably from about 1.390 inches to about 1.600 inches,and more preferably from about 1.500 inches to about 1.600 inches. Inyet another embodiment, the core has a diameter of about 1.550 inches toabout 1.650 inches.

The core of the golf ball may also be extremely large in relation to therest of the ball. For example, in one embodiment, the core makes upabout 90 percent to about 98 percent of the ball, preferably about 94percent to about 96 percent of the ball. In this embodiment, thediameter of the core is preferably about 1.540 inches or greater,preferably about 1.550 inches or greater. In one embodiment, the corediameter is about 1.590 inches or greater. In another embodiment, thediameter of the core is about 1.640 inches or less.

When the core includes an inner core layer and an outer core layer, theinner core layer is preferably about 0.9 inches or greater and the outercore layer preferably has a thickness of about 0.1 inches or greater. Inone embodiment, the inner core layer has a diameter from about 0.09inches to about 1.2 inches and the outer core layer has a thickness fromabout 0.1 inches to about 0.8 inches. In yet another embodiment, theinner core layer diameter is from about 0.095 inches to about 1.1 inchesand the outer core layer has a thickness of about 0.20 inches to about0.03 inches.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics, and durability. In one embodiment, thecover thickness is from about 0.02 inches to about 0.35 inches. Thecover preferably has a thickness of about 0.02 inches to about 0.12inches, preferably about 0.1 inches or less. When the compositions ofthe invention are used to form the outer cover of a golf ball, the covermay have a thickness of about 0.1 inches or less, preferably about 0.07inches or less. In one embodiment, the outer cover has a thickness fromabout 0.02 inches to about 0.07 inches. In another embodiment, the coverthickness is about 0.05 inches or less, preferably from about 0.02inches to about 0.05 inches. In yet another embodiment, the outer coverlayer is between about 0.02 inches to about 0.045 inches. In stillanother embodiment, the outer cover layer is about 0.025 to about 0.04inches thick. In one embodiment, the outer cover layer is about 0.03inches thick.

The range of thicknesses for an intermediate layer of a golf ball islarge because of the vast possibilities when using an intermediatelayer, i.e., as an outer core layer, an inner cover layer, a woundlayer, a moisture/vapor barrier layer. When used in a golf ball of theinvention, the intermediate layer, or inner cover layer, may have athickness about 0.3 inches or less. In one embodiment, the thickness ofthe intermediate layer is from about 0.002 inches to about 0.1 inches,preferably about 0.01 inches or greater. In one embodiment, thethickness of the intermediate layer is about 0.09 inches or less,preferably about 0.06 inches or less. In another embodiment, theintermediate layer thickness is about 0.05 inches or less, morepreferably about 0.01 inches to about 0.045 inches. In one embodiment,the intermediate layer, thickness is about 0.02 inches to about 0.04inches. In another embodiment, the intermediate layer thickness is fromabout 0.025 inches to about 0.035 inches. In yet another embodiment, thethickness of the intermediate layer is about 0.035 inches thick. Instill another embodiment, the inner cover layer is from about 0.03inches to about 0.035 inches thick. Varying combinations of these rangesof thickness for the intermediate and outer cover layers may be used incombination with other embodiments described herein.

The ratio of the thickness of the intermediate layer to the outer coverlayer is preferably about 10 or less, preferably from about 3 or less.In another embodiment, the ratio of the thickness of the intermediatelayer to the outer cover layer is about 1 or less.

The core and intermediate layer(s) together form an inner ballpreferably having a diameter of about 1.48 inches or greater for a1.68-inch ball. In one embodiment, the inner ball of a 1.68-inch ballhas a diameter of about 1.52 inches or greater. In another embodiment,the inner ball of a 1.68-inch ball has a diameter of about 1.66 inchesor less. In yet another embodiment, a 1.72-inch (or more) ball has aninner ball diameter of about 1.50 inches or greater. In still anotherembodiment, the diameter of the inner ball for a 1.72-inch ball is about1.70 inches or less.

Hardness

The molding process and composition of golf ball portions typicallyresults in a gradient of material properties. Methods employed in theprior art generally exploit hardness to quantify these gradients. Mostgolf balls consist of layers having different hardnesses, e.g., hardnessgradients, to achieve desired performance characteristics. The presentinvention contemplates golf balls having hardness gradients betweenlayers, as well as those golf balls with layers having the samehardness.

It should be understood, especially to one of ordinary skill in the art,that there is a fundamental difference between “material hardness” and“hardness, as measured directly on a golf ball.” Material hardness isdefined by the procedure set forth in ASTM-D2240 and generally involvesmeasuring the hardness of a flat “slab” or “button” formed of thematerial of which the hardness is to be measured. Hardness, whenmeasured directly on a golf ball (or other spherical surface) is acompletely different measurement and, therefore, results in a differenthardness value. This difference results from a number of factorsincluding, but not limited to, ball construction (i.e., core type,number of core and/or cover layers, etc.), ball (or sphere) diameter,and the material composition of adjacent layers. Hardness is aqualitative measure of static modulus and does not represent the modulusof the material at the deformation rates associated with golf ball use,i.e., impact by a club. As is well known to one skilled in the art ofpolymer science, the time-temperature superposition principle may beused to emulate alternative deformation rates. For golf ball portionsincluding polybutadiene, a 1-Hz oscillation at temperatures between 0°C. and −50° C. are believed to be qualitatively equivalent to golf ballimpact rates. Therefore, measurement of loss tangent and dynamicstiffness at 0° C. to −50° C. may be used to accurately anticipate golfball performance, preferably at temperatures between about −20° C. and−50° C. It should also be understood that the two measurement techniquesare not linearly related and, therefore, one hardness value cannoteasily be correlated to the other.

The cores of the present invention may have varying hardnesses dependingon the particular golf ball construction. In one embodiment, the corehardness is at least about 15 Shore A, preferably about 30 Shore A, asmeasured on a formed sphere. In another embodiment, the core has ahardness of about 50 Shore A to about 90 Shore D. In yet anotherembodiment, the hardness of the core is about 80 Shore D or less.Preferably, the core has a hardness about 30 to about 65 Shore D, andmore preferably, the core has a hardness about 35 to about 60 Shore D.

When a composition of the present invention is incorporated into a core,the core may have a hardness gradient, i.e., a first hardness at a firstpoint, i.e., at an interior location, and a second hardness at a secondpoint, i.e., at an exterior surface, as measured on a molded sphere. Inone embodiment, the second hardness is at least about 6 percent greaterthan the first hardness, preferably about 10 percent greater than thefirst hardness. In other embodiments, the second hardness is at leastabout 20 percent greater or at least about 30 percent greater, than thefirst hardness.

For example, the interior of the core may have a first hardness of about45 Shore C to about 60 Shore C and the exterior surface of the core mayhave a second hardness of about 65 Shore C to about 75 Shore C. In onegolf ball formulated according to the invention, the first hardness wasabout 51 Shore C and a second hardness was about 71 Shore C, providing ahardness difference of greater than 20 percent.

In one embodiment, however, the core has a substantially uniformhardness throughout. Thus, in this aspect, the first and second hardnesspreferably differ by about 5 percent or less, more preferably about 3percent or less, and even more preferably by about 2 percent or less. Inanother embodiment, the hardness is uniform throughout the component.

The intermediate layer(s) of the present invention may also vary inhardness depending on the specific construction of the ball. In oneembodiment, the hardness of the intermediate layer is about 30 Shore Dor greater. In another embodiment, the hardness of the intermediatelayer is about 90 Shore D or less, preferably about 80 Shore D or less,and more preferably about 70 Shore D or less. In yet another embodiment,the hardness of the intermediate layer is about 50 Shore D or greater,preferably about 55 Shore D or greater. In one embodiment, theintermediate layer hardness is from about 55 Shore D to about 65 ShoreD. The intermediate layer may also be about 65 Shore D or greater.

When the intermediate layer is intended to be harder than the corelayer, the ratio of the intermediate layer hardness to the core hardnesspreferably about 2 or less. In one embodiment, the ratio is about 1.8 orless. In yet another embodiment, the ratio is about 1.3 or less.

As with the core and intermediate layers, the cover hardness may varydepending on the construction and desired characteristics of the golfball. The ratio of cover hardness to inner ball hardness is a primaryvariable used to control the aerodynamics of a ball and, in particular,the spin of a ball. In general, the harder the inner ball, the greaterthe driver spin and the softer the cover, the greater the driver spin.

For example, when the intermediate layer is intended to be the hardestpoint in the ball, e.g., about 50 Shore D to about 75 Shore D, the covermaterial may have a hardness of about 20 Shore D or greater, preferablyabout 25 Shore D or greater, and more preferably about 30 Shore D orgreater, as measured on the slab. In another embodiment, the coveritself has a hardness of about 30 Shore D or greater. In particular, thecover may be from about 30 Shore D to about 60 Shore D. In oneembodiment, the cover has a hardness of about 40 Shore D to about 65Shore D. In another embodiment, the cover has a hardness less than about45 Shore D, preferably less than about 40 Shore D, and more preferablyabout 25 Shore D to about 40 Shore D. In one embodiment, the cover has ahardness from about 30 Shore D to about 40 Shore D. In yet anotherembodiment, the cover hardness is from about 35 to 80 Shore D,preferably from about 40 to 75 Shore D, and more preferably from about45 to 70 Shore D.

In this embodiment when the outer cover layer is softer than theintermediate layer or inner cover layer, the ratio of the Shore Dhardness of the outer cover material to the intermediate layer materialis about 0.8 or less, preferably about 0.75 or less, and more preferablyabout 0.7 or less. In another embodiment, the ratio is about 0.5 orless, preferably about 0.45 or less.

In yet another embodiment, the ratio is about 0.1 or less when the coverand intermediate layer materials have hardnesses that are substantiallythe same. When the hardness differential between the cover layer and theintermediate layer is not intended to be as significant, the cover mayhave a hardness of about 55 Shore D to about 65 Shore D. In thisembodiment, the ratio of the Shore D hardness of the outer cover to theintermediate layer is about 1.0 or less, preferably about 0.9 or less.

The cover hardness may also be defined in terms of Shore C. For example,the cover may have a hardness of about 70 Shore C or greater, preferablyabout 80 Shore C or greater. In another embodiment, the cover has ahardness of about 95 Shore C or less, preferably about 90 Shore C orless.

In another embodiment, the cover layer is harder than the intermediatelayer. In this design, the ratio of Shore D hardness of the cover layerto the intermediate layer is about 1.33 or less, preferably from about1.14 or less.

When a two-piece ball is constructed, the core may be softer than theouter cover. For example, the core hardness may range from about 30Shore D to about 50 Shore D, and the cover hardness may be from about 50Shore D to about 75 Shore D. In this type of construction, the ratiobetween the cover hardness and the core hardness is preferably about1.75 or less. In another embodiment, the ratio is about 1.55 or less.Depending on the materials, for example, if a composition of theinvention is acid-functionalized wherein the acid groups are at leastpartially neutralized, the hardness ratio of the cover to core ispreferably about 1.25 or less.

Compression

Depending on the desired properties, balls prepared according to theinvention can exhibit substantially the same or higher resilience, orcoefficient of restitution (CoR), with a decrease in compression ormodulus, compared to balls of conventional construction. As used herein,the term “coefficient of restitution” (CoR) is calculated by dividingthe rebound velocity of the golf ball by the incoming velocity when agolf ball is shot out of an air cannon. The CoR testing is conductedover a range of incoming velocities and determined at an inboundvelocity of 125 ft/s. Additionally, balls prepared according to theinvention can also exhibit substantially higher resilience, orcoefficient of restitution (CoR), without an increase in compression,compared to balls of conventional construction. Another measure of thisresilience is the “loss tangent,” or tan δ, which is obtained whenmeasuring the dynamic stiffness of an object. Loss tangent andterminology relating to such dynamic properties is typically describedaccording to ASTM D4092-90. Thus, a lower loss tangent indicates ahigher resiliency, thereby indicating a higher rebound capacity. Lowloss tangent indicates that most of the energy imparted to a golf ballfrom the club is converted to dynamic energy, i.e., launch velocity andresulting longer distance. The rigidity or compressive stiffness of agolf ball may be measured, for example, by the dynamic stiffness. Ahigher dynamic stiffness indicates a higher compressive stiffness. Toproduce golf balls having a desirable compressive stiffness, the dynamicstiffness of the crosslinked reaction product material should be lessthan about 50,000 N/m at −50° C. Preferably, the dynamic stiffnessshould be between about 10,000 and 40,000 N/m at −50° C., morepreferably, the dynamic stiffness should be between about 20,000 and30,000 N/m at −50° C.

The dynamic stiffness is similar in some ways to dynamic modulus.Dynamic stiffness is dependent on probe geometry as described herein,whereas dynamic modulus is a unique material property, independent ofgeometry. The dynamic stiffness measurement has the unique attribute ofenabling quantitative measurement of dynamic modulus and exactmeasurement of loss tangent at discrete points within a sample article.In the case of this invention, the article is a golf ball core. Thereaction product preferably has a loss tangent below about 0.1 at −50°C., and more preferably below about 0.07 at −50° C.

There is currently no USGA limit on the CoR of a golf ball, but theinitial velocity of the golf ball cannot exceed 250±5 feet/second(ft/s). Thus, in one embodiment, the initial velocity is about 245 ft/sor greater and about 255 ft/s or less. In another embodiment, theinitial velocity is about 250 ft/s or greater. In one embodiment, theinitial velocity is about 250 ft/s to about 255 ft/s. In anotherembodiment, the initial velocity is about 253 ft/s to about 254 ft/s. Inyet another embodiment, the initial velocity is about 255 ft/s. Whilethe current rules on initial velocity require that golf ballmanufacturers stay within the limit, one of ordinary skill in the artwould appreciate that the golf ball of the invention would readilyconvert into a golf ball with initial velocity outside of this range.

As a result, of the initial velocity limitation set forth by the USGA,the goal is to maximize CoR without violating the 255 ft/s limit. In aone-piece solid golf ball, the CoR will depend on a variety ofcharacteristics of the ball, including its composition and hardness. Fora given composition, CoR will generally increase as hardness isincreased. In a two-piece solid golf ball, e.g., a core and a cover, oneof the purposes of the cover is to produce a gain in CoR over that ofthe core. When the contribution of the core to high CoR is substantial,a lesser contribution is required from the cover. Similarly, when thecover contributes substantially to high CoR of the ball, a lessercontribution is needed from the core.

The resultant golf balls typically have a coefficient of restitution ofgreater than about 0.7, preferably greater than about 0.75, and morepreferably greater than about 0.78. In one embodiment, golf balls thathave a CoR from about 0.7 to about 0.820. In another embodiment, theball has a CoR of about 0.780 or greater. In addition, the inner ballpreferably has a CoR of about 0.800 or more. In one embodiment, the CoRis about 0.815 or greater.

The golf balls also typically have an Atti compression (which has beenreferred to as PGA compression in the past) of at least about 40,preferably from about 50 to 120, and more preferably from about 60 to100. Preferably, golf balls have an Atti compression of 80 or greater,more preferably 90 or greater, most preferably 95 or greater. As usedherein, the term “Atti compression” is defined as the deflection of anobject or material relative to the deflection of a calibrated spring, asmeasured with an Atti Compression Gauge, that is commercially availablefrom Atti Engineering Corp. of Union City, N.J. Atti compression istypically used to measure the compression of a golf ball and/or a golfball core. Compression values are dependent on the diameter of thearticle being measured. The golf ball polybutadiene material of thepresent invention typically has a flexural modulus of from about 500 psito 300,000 psi, preferably from of at least about 15 Shore A, preferablybetween about 30 Shore A and 80 Shore D, more preferably between about50 Shore A and 60 Shore D. The specific gravity is typically greaterthan about 0.7, preferably greater than about 1, for the golf ballpolybutadiene material. The dynamic shear storage modulus, or storagemodulus, of the golf ball polybutadiene material at about 23° C. istypically at least about 10,000 dyn/cm², preferably from about 10⁴-10¹⁰dyn/cm², more preferably from about 10⁶ to 10¹⁰ dyn/cm².

Compression values are dependent on the diameter of the component beingmeasured. The Atti compression of the core, or portion of the core, ofgolf balls prepared according to the invention is preferably less thanabout 80, more preferably less than about 75. In another embodiment, thecore compression is from about 40 to about 80, preferably from about 50to about 70. In yet another embodiment, the core compression ispreferably below about 50, and more preferably below about 25. In yetanother embodiment, the core compression is zero or negative compression(i.e., below zero).

In an alternative, low compression embodiment, the core has acompression less than about 20, more preferably less than about 10, andmost preferably, 0. As known to one of ordinary skill in the art,however, the cores generated according to the present invention may bebelow the measurement of the Atti Compression Gauge. In an embodimentwhere the core is hard, the compression may be about 90 or greater. Inone embodiment, the compression of the hard core ranges from about 90 toabout 100.

The core of the present invention may also have a Soft Center DeflectionIndex (SCDI) compression of less than about 160, preferably betweenabout 40 and about 160, and more preferably, between about 60 and about120.

Flexural Modulus

Accordingly, it is preferable that the golf balls of the presentinvention have an intermediate layer with a flexural modulus of about500 psi to about 500,000 psi. More preferably, the flexural modulus ofthe intermediate layer is about 2,000 psi to about 200,000 psi. Mostpreferably, the flexural modulus of the intermediate layer is about2,000 psi to about 200,000 psi. Flexural modulus is a material propertythat measures the flexural modulus of the material itself, rather thanbeing a measurement of the golf ball or component (i.e., cover,intermediate layer or core). For example, the flexural modulus of acover, as referred to herein, is a measurement of the flexural modulusof the materials that comprise the cover, rather than the cover itself.Likewise, the flexural modulus of the intermediate layer, as referred toherein, is a measurement of the flexural modulus of the materials thatcomprise the intermediate layer, rather than the cover itself.

The flexural modulus of the cover on the golf balls, as measured by ASTMmethod D-790, is typically greater than about 500 psi, and is preferablyfrom about 500 psi to about 150,000 psi. The flexural moduli of thecover layer is preferably about 2,000 psi or greater, and morepreferably about 5,000 psi or greater. In one embodiment, the flexuralmoduli of the cover is from about 5,000 psi to about 100,000 psi, morepreferably from about 15,000 psi to about 80,000 psi, and mostpreferably from about 18,000 psi to about 65,000 psi. In anotherembodiment, the flexural moduli of the cover layer is about 100,000 psior less, preferably about 80,000 or less, and more preferably about70,000 psi or less. In one embodiment, when the cover layer has ahardness of about 50 Shore D to about 60 Shore D, the cover layerpreferably has a flexural modulus of about 55,000 psi to about 65,000psi.

In one embodiment, the ratio of the flexural modulus of the intermediatelayer to the cover layer is about 0.003 to about 50. In anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.006 to about 4.5. In yet anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.11 to about 4.5.

In one embodiment, the compositions of the invention are used in a golfball with multiple cover layers having essentially the same hardness,but differences in flexural moduli. In this aspect of the invention, thedifference between the flexural moduli of the two cover layers ispreferably about 5,000 psi or less. In another embodiment, thedifference in flexural moduli is about 500 psi or greater. In yetanother embodiment, the difference in the flexural moduli between thetwo cover layers, wherein at least one is reinforced is about 500 psi toabout 10,000 psi, preferably from about 500 psi to about 5,000 psi. Inone embodiment, the difference in flexural moduli between the two coverlayers formed of unreinforced or unmodified materials is about 1,000 psito about 2,500 psi.

Specific Gravity

The specific gravity of a cover or intermediate layer including thecompositions of the invention is preferably at least about 0.7. Thespecific gravity of a cover including the compositions of the inventionis from about 0.8 to about 1.15, preferably from about 0.9 to about1.10, and more preferably from about 0.95 to about 1.05. The specificgravity of an intermediate layer including the compositions of theinvention is from about 0.9 to about 5.0, preferably from about 0.95 toabout 4, and more preferably from about 1.0 to about 3.0.

In another embodiment, the specific gravity of a cover or intermediatelayer including the compositions of the invention is at least about 0.6.In yet another embodiment, the specific gravity of the cover orintermediate layer is at last about 1.0, preferably at least about 0.9and more preferably at least about 0.8.

The specific gravity of a core including the compositions of theinvention is greater than 1.5, more preferably greater than 1.8 and morepreferably greater than 2.0. In another embodiment, the specific gravityof the fore including the compositions of the invention is greater than2.5, and can be as high as 5.0 and 10.0.

Ball Spin

A spin rate of a golf ball refers to the speed it spins on an axis whilein flight, measured in revolutions per minute (“rpm”). Spin generateslift, and accordingly, spin rate directly influences how high the ballflies and how quickly it stops after landing. The golf balls disclosedherein can be tested to determine spin rate by initially establishingtest conditions using suitable control golf balls and golf clubs. Forexample, a spin rate of a golf ball struck by a standard golf driver wasobtained by using test conditions for a Titleist Pinnacle Gold golf ballthat gives a ball speed of about 159 to about 161 miles/hour, a launchangle of about 9.0 degrees to about 10.0 degrees, and a spin rate ofabout 2900 rpm to about 3100 rpm. Thus in one embodiment, the spin rateof a golf ball hit with a golf club driver under such test conditions isbetween about 2,000 rpm to about 4,000 rpm. In a preferred embodiment,the spin rate of a golf ball hit with a golf club driver is betweenabout 2,500 rpm to about 3,500 rpm,-more preferably between about 2,800and 3,200 rpm.

For an 8-iron ball spin test, a spin rate of a golf ball struck by astandard 8-iron club was obtained by using test conditions for aTitleist Pro V1 golf ball that gives a ball speed of about 114 to about116 miles/hour, a launch angle of about 18.5 to about 19.5 degrees and aspin rate of about 8100 rpm to about 8300 rpm. Thus in one embodiment,the spin rate of cleanly struck 8-iron shot under such test conditionsis between 6,500 rpm and 10,000 rpm. In preferred embodiment, the spinrate of an average, cleanly struck 8-iron shot is between 7,500 rpm and9,000 rpm, more preferably between about 8,000 rpm and 9,000 rpm.

EXAMPLES Example 1 Golf ball cores comprising ZnPCTP and ZDMA

Golf ball cores were formed, using methods well known in the art, withcompositions that comprised ZDMA and ZnPCTP. In particular, the golfball cores comprised BUNA® CB-23 polybutadiene (Bayer of Akron Ohio.),zinc oxide, AKTIPLAST PP (Rhein Chemie Rheinau GmbH of Germany),PERKADOX® BC (Akzo Noble Polymer Chemicals of Chicago, Ill.), SR-365ZDMA (Sartomer Company, Inc. of Exton, Pa.) and ZnPCTP (eChinachem ofSan Francisco, Calif.). The following chart shows core compositions madein accordance to the present invention and their corresponding corecompression and CoR at 125 fps. All amounts listed in the chart are inpph.

TABLE 1 Core Formulations Having ZnPCTP and ZDMA 1 2 3 4 5 6 7 BUNA® CB-23 100 100 100 100 100 100 100 Zinc Oxide 5.0 5.0 5.0 5.0 5.0 5.05.0 AKTIPLAST ® PP 5.0 5.0 5.0 5.0 5.0 5.0 5.0 PERKADOX ® BC 0.50 0.500.50 0.50 0.50 0.50 0.50 SR-365 (ZDMA) 28.0 34.0 40.0 46.0 40.0 46.052.0 ZnPCTP 0 0 0 0 2.35 2.35 2.35 S'max 23.57 28.76 35.91 45.87 27.5734.53 52.31 TC90 (min:sec) 10:55 10:40 10:39 10:21 9:01 9:41 9:38Compression — 2 23 46 31 54 87 CoR @ 125 fps 0.7295 0.7370 0.7406 0.74400.7810 0.7864 0.8106

In addition, the following table shows comparative core formulationsthat contain ZDA instead of ZDMA. In particular, the golf ball corescomprised BUNA® CB-23 polybutadiene (Bayer of Akron Ohio.), zinc oxide,AKTIPLAST PP (Rhein Chemie Rheinau GmbH of Germany), PERKADOX® BC (AkzoNoble Polymer Chemicals of Chicago, Ill.), SR-705 ZDA (Sartomer Company,Inc. of Exton, Pa.) and ZnPCTP (eChinachem of San Francisco, Calif.).

TABLE 2 Comparative Core Formulations Having ZDA 8 9 10 11 BUNA ® CB-23100 100 100 100 Zinc Oxide 5.0 5.0 5.0 5.0 AKTIPLAST ® PP 5.0 5.0 5.05.0 PERKADOX ® BC 0.50 0.50 0.50 0.50 SR-365 (ZDA) 25.0 30.0 30.0 35.0ZnPCTP 0 0 2.35 2.35 S'max 65.35 88.09 50.49 68.44 TC90 (min:sec) 8:468:00 13:11 13:24 Compression 62 84 60 77 CoR @ 125 fps 0.8106 0.81960.8242 0.8275

The addition of ZnPCTP gives an unexpected effect in ZDMA-containingcompositions when compared with ZDA-containing compositions.Formulations 8 and 9 of Table 2 show that increases in ZDA amountsresult in significant increases in core compression, but the addition ofZnPCTP (comparing Formulations 9 and 10) lowers core compression whileexhibiting a small increase in CoR @ 125 fps and a large increase in theTC90 time. Formulations 1-4 in Table 1 show that increases in ZDMAamounts result in significant increases in core compression, but theaddition of ZnPCTP unexpectedly increases core compression whileexhibiting large increases in CoR @ 125 fps and small decreases in TC90times (Formulations 5-8). Further, the combination of ZDMA and ZnPCTPprovides for CoR values that are suitable for golf ball cores.

The invention described and claimed herein is not to be limited in scopeby the specific embodiments herein disclosed, since these embodimentsare intended as illustrations of several aspects of the invention. Anyequivalent embodiments are intended to be within the scope of thisinvention. Indeed, various modifications of the invention in addition tothose shown and described herein will become apparent to those skilledin the art from the foregoing description. For example, the compositionsof the present invention may be used in a variety of golf equipment, forexample, golf shoes for sole applications, as well as in inserts forgolf putters. Such modifications are also intended to fall within thescope of the appended claims.

1. A golf ball comprising a core and a cover, wherein the core is formedfrom a composition comprising: a resilient polymer component comprisingpolybutadiene, polyisoprene, thermoplastic copolyesterester blockcopolymer; dynamically vulcanized thermoplastic elastomer; hydrogenatedstyrene-butadiene elastomer, non-hydrogenated styrene-butadieneelastomer; thermoplastic polyurethane; polymers made using a metallocenecatalyst; ethylene propylenediene monomer; ethylene propylene rubber, ormixtures thereof, a free radical source, about 15 to 25 pph zincdimethacrylate; about 25 to 35 pph co-crosslinking agent; and about 2 to5 pph of at least one metal salt of a halogenated organosulfur compoundhaving the following general formula I:

wherein at least one of R₁-R₅ comprises a halogen group, and wherein theremainder of R₁-R₅ is selected from the group consisting of substitutedor unsubstituted C₁-C₈ alkyl groups; halogen groups; thiol groups (—SH),carboxylated groups; sulfonated groups; and hydrogen; in any order,wherein the metal salt comprises Zn, Ca, Ba, Cd, Sn, Mg, or Mn, andwherein the core has a compression of about 75 to 90 atti, and whereinthe cover comprises a thermoset polyurethane, thermoplasticpolyurethane, thermoset polyurea, or thermoplastic polyurea.
 2. The golfball of claim 1, wherein the golf ball further comprises an intermediatelayer disposed between the core and the cover.
 3. The golf ball of claim2, wherein the flexural modulus of the intermediate layer is about 2000psi to about 200,000 psi and the flexural modulus of the cover is fromabout 5000 psi to about 100,000 psi.
 4. The golf ball of claim 1,wherein the at least one halogenated organosulfur compound of formula Iis present in an amount of about 2 pph to about 3 pph.
 5. The golf ballof claim 2, wherein the core has a hardness of about 15 Shore A orgreater, the intermediate layer has a hardness of about 30 Shore D orgreater, and the cover has a hardness of 70 Shore D or less.
 6. The golfball of claim 1, wherein the at least one halogenated organosulfurcompound of formula I is a zinc salt of pentafluorothiophenol;2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol;2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol;3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;or 2,3,5,6-tetraiodothiophenol.
 7. The golf ball of claim 1, wherein theat least one metal salt of a halogenated organosulfur compound ispresent in an amount of about 3 pph to about 5 pph.
 8. The golf ball ofclaim 1, wherein the at least one halogenated organosulfur compound offormula I is a metal salt of Zn.
 9. The golf ball of claim 8, whereinthe at least one halogenated organosulfur compound of formula I is zincpentachlorothiophenol.
 10. The golf ball of claim 1, wherein the freeradical source is selected from the group consisting of di-tert-amylperoxide, di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and any mixture thereof.
 11. Thegolf ball of claim 1, wherein the co-crosslinking agent comprises anorganic acid comprising more than one carboxylic acid group.
 12. Thegolf ball of claim 1, wherein the cover comprises a castable reactiveliquid material.
 13. The golf ball of claim 1, wherein the golf ball hasa coefficient of restitution of at least about 0.78.
 14. The golf ballof claim 1, wherein the golf ball has a ball spin rate of about 2500 rpmto about 4000 rpm when the golf ball is hit with a golf driver.
 15. Thegolf ball of claim 1, wherein the golf ball has a ball spin rate ofabout 6,500 rpm to about 10,000 rpm when the golf ball is hit with an8-iron.
 16. The golf ball of claim 1, wherein the resilient polymercomponent has a Mooney viscosity from about 30 to about
 120. 17. A golfball comprising a core and a cover, wherein at least one structurallayer is formed from a composition comprising: a resilient polymercomponent, a free radical source, about 15 to 25 pph zincdimethacrylate; an organic acid comprising more than one carboxylic acidgroup; and about 2 to 5 pph zinc pentachlorothiophenol, wherein the corehas a compression of about 75 to 90 atti, and wherein the covercomprises a castable reactive liquid material.
 18. The golf ball ofclaim 17, wherein the at least one structural layer is a core layer. 19.The golf ball of claim 17, wherein the at least one metal salt of ahalogenated organosulfur compound is present in an amount of about 2 pphto about 3 pph.
 20. The golf ball of claim 17, wherein the at least onemetal salt of a halogenated organosulfur compound is present in anamount of about 3 pph to about 5 pph.
 21. The golf ball of claim 17,wherein the organic acid is present in an amount greater than about 10pph of the base polymer.
 22. A method of manufacturing golf ballscomprising: providing a core having a compression of about 75 to 90atti; optionally providing an intermediate layer disposed outside thecore; and providing at least one cover over the core and optionalintermediate layer, wherein the cover comprises a thermosetpolyurethane, a thermoplastic polyurethane, a thermoset polyurea, or athermoplastic polyurea, wherein at least one of the core and theoptional intermediate layer comprises at least one layer formed from acomposition comprising: a resilient polymer component, a free radicalsource, about 15 to 25 pph zinc dimethacrylate; about 25 to about 35 pphco-crosslinking agent; and about 2 to 3 pph of a metal salt of ahalogenated organosulfur compound having the following general formulaI:

wherein at least one of R₁-R₅ comprises halogen, and wherein theremainder of R₁-R₅ is selected from the group consisting of substitutedor unsubstituted C₁-C₈ alkyl groups; halogen groups; thiol groups (—SH),carboxylated groups; sulfonated groups; and hydrogen; in any order,wherein the metal salt comprises Zn, Ca, Ba, Cd, Sn, Mg, or Mn.
 23. Themethod of claim 22, wherein the co-crosslinking agent comprises anorganic acid comprising more than one carboxylic acid group.